diff options
| -rw-r--r-- | pkg/tcpip/header/ipv6.go | 9 | ||||
| -rw-r--r-- | pkg/tcpip/network/ipv4/icmp.go | 33 | ||||
| -rw-r--r-- | pkg/tcpip/network/ipv4/ipv4.go | 29 | ||||
| -rw-r--r-- | pkg/tcpip/network/ipv6/icmp.go | 32 | ||||
| -rw-r--r-- | pkg/tcpip/network/ipv6/ipv6.go | 29 |
5 files changed, 116 insertions, 16 deletions
diff --git a/pkg/tcpip/header/ipv6.go b/pkg/tcpip/header/ipv6.go index 4e7e5f76a..55d09355a 100644 --- a/pkg/tcpip/header/ipv6.go +++ b/pkg/tcpip/header/ipv6.go @@ -54,7 +54,7 @@ type IPv6Fields struct { // NextHeader is the "next header" field of an IPv6 packet. NextHeader uint8 - // HopLimit is the "hop limit" field of an IPv6 packet. + // HopLimit is the "Hop Limit" field of an IPv6 packet. HopLimit uint8 // SrcAddr is the "source ip address" of an IPv6 packet. @@ -171,7 +171,7 @@ func (b IPv6) PayloadLength() uint16 { return binary.BigEndian.Uint16(b[IPv6PayloadLenOffset:]) } -// HopLimit returns the value of the "hop limit" field of the ipv6 header. +// HopLimit returns the value of the "Hop Limit" field of the ipv6 header. func (b IPv6) HopLimit() uint8 { return b[hopLimit] } @@ -236,6 +236,11 @@ func (b IPv6) SetDestinationAddress(addr tcpip.Address) { copy(b[v6DstAddr:][:IPv6AddressSize], addr) } +// SetHopLimit sets the value of the "Hop Limit" field. +func (b IPv6) SetHopLimit(v uint8) { + b[hopLimit] = v +} + // SetNextHeader sets the value of the "next header" field of the ipv6 header. func (b IPv6) SetNextHeader(v uint8) { b[IPv6NextHeaderOffset] = v diff --git a/pkg/tcpip/network/ipv4/icmp.go b/pkg/tcpip/network/ipv4/icmp.go index 9b5e37fee..58a19e74a 100644 --- a/pkg/tcpip/network/ipv4/icmp.go +++ b/pkg/tcpip/network/ipv4/icmp.go @@ -290,6 +290,13 @@ type icmpReasonProtoUnreachable struct{} func (*icmpReasonProtoUnreachable) isICMPReason() {} +// icmpReasonTTLExceeded is an error where a packet's time to live exceeded in +// transit to its final destination, as per RFC 792 page 6, Time Exceeded +// Message. +type icmpReasonTTLExceeded struct{} + +func (*icmpReasonTTLExceeded) isICMPReason() {} + // icmpReasonReassemblyTimeout is an error where insufficient fragments are // received to complete reassembly of a packet within a configured time after // the reception of the first-arriving fragment of that packet. @@ -342,11 +349,31 @@ func (p *protocol) returnError(reason icmpReason, pkt *stack.PacketBuffer) *tcpi return nil } + // If we hit a TTL Exceeded error, then we know we are operating as a router. + // As per RFC 792 page 6, Time Exceeded Message, + // + // If the gateway processing a datagram finds the time to live field + // is zero it must discard the datagram. The gateway may also notify + // the source host via the time exceeded message. + // + // ... + // + // Code 0 may be received from a gateway. ... + // + // Note, Code 0 is the TTL exceeded error. + // + // If we are operating as a router/gateway, don't use the packet's destination + // address as the response's source address as we should not not own the + // destination address of a packet we are forwarding. + localAddr := origIPHdrDst + if _, ok := reason.(*icmpReasonTTLExceeded); ok { + localAddr = "" + } // Even if we were able to receive a packet from some remote, we may not have // a route to it - the remote may be blocked via routing rules. We must always // consult our routing table and find a route to the remote before sending any // packet. - route, err := p.stack.FindRoute(pkt.NICID, origIPHdrDst, origIPHdrSrc, ProtocolNumber, false /* multicastLoop */) + route, err := p.stack.FindRoute(pkt.NICID, localAddr, origIPHdrSrc, ProtocolNumber, false /* multicastLoop */) if err != nil { return err } @@ -454,6 +481,10 @@ func (p *protocol) returnError(reason icmpReason, pkt *stack.PacketBuffer) *tcpi icmpHdr.SetType(header.ICMPv4DstUnreachable) icmpHdr.SetCode(header.ICMPv4ProtoUnreachable) counter = sent.DstUnreachable + case *icmpReasonTTLExceeded: + icmpHdr.SetType(header.ICMPv4TimeExceeded) + icmpHdr.SetCode(header.ICMPv4TTLExceeded) + counter = sent.TimeExceeded case *icmpReasonReassemblyTimeout: icmpHdr.SetType(header.ICMPv4TimeExceeded) icmpHdr.SetCode(header.ICMPv4ReassemblyTimeout) diff --git a/pkg/tcpip/network/ipv4/ipv4.go b/pkg/tcpip/network/ipv4/ipv4.go index 0c828004a..b4f21d61e 100644 --- a/pkg/tcpip/network/ipv4/ipv4.go +++ b/pkg/tcpip/network/ipv4/ipv4.go @@ -485,6 +485,16 @@ func (e *endpoint) WriteHeaderIncludedPacket(r *stack.Route, pkt *stack.PacketBu // forwardPacket attempts to forward a packet to its final destination. func (e *endpoint) forwardPacket(pkt *stack.PacketBuffer) *tcpip.Error { h := header.IPv4(pkt.NetworkHeader().View()) + ttl := h.TTL() + if ttl == 0 { + // As per RFC 792 page 6, Time Exceeded Message, + // + // If the gateway processing a datagram finds the time to live field + // is zero it must discard the datagram. The gateway may also notify + // the source host via the time exceeded message. + return e.protocol.returnError(&icmpReasonTTLExceeded{}, pkt) + } + dstAddr := h.DestinationAddress() // Check if the destination is owned by the stack. @@ -503,13 +513,22 @@ func (e *endpoint) forwardPacket(pkt *stack.PacketBuffer) *tcpip.Error { } defer r.Release() - // TODO(b/143425874) Decrease the TTL field in forwarded packets. + // We need to do a deep copy of the IP packet because + // WriteHeaderIncludedPacket takes ownership of the packet buffer, but we do + // not own it. + newHdr := header.IPv4(stack.PayloadSince(pkt.NetworkHeader())) + + // As per RFC 791 page 30, Time to Live, + // + // This field must be decreased at each point that the internet header + // is processed to reflect the time spent processing the datagram. + // Even if no local information is available on the time actually + // spent, the field must be decremented by 1. + newHdr.SetTTL(ttl - 1) + return r.WriteHeaderIncludedPacket(stack.NewPacketBuffer(stack.PacketBufferOptions{ ReserveHeaderBytes: int(r.MaxHeaderLength()), - // We need to do a deep copy of the IP packet because - // WriteHeaderIncludedPacket takes ownership of the packet buffer, but we do - // not own it. - Data: stack.PayloadSince(pkt.NetworkHeader()).ToVectorisedView(), + Data: buffer.View(newHdr).ToVectorisedView(), })) } diff --git a/pkg/tcpip/network/ipv6/icmp.go b/pkg/tcpip/network/ipv6/icmp.go index 8502b848c..8d788af80 100644 --- a/pkg/tcpip/network/ipv6/icmp.go +++ b/pkg/tcpip/network/ipv6/icmp.go @@ -750,6 +750,12 @@ type icmpReasonPortUnreachable struct{} func (*icmpReasonPortUnreachable) isICMPReason() {} +// icmpReasonHopLimitExceeded is an error where a packet's hop limit exceeded in +// transit to its final destination, as per RFC 4443 section 3.3. +type icmpReasonHopLimitExceeded struct{} + +func (*icmpReasonHopLimitExceeded) isICMPReason() {} + // icmpReasonReassemblyTimeout is an error where insufficient fragments are // received to complete reassembly of a packet within a configured time after // the reception of the first-arriving fragment of that packet. @@ -794,11 +800,27 @@ func (p *protocol) returnError(reason icmpReason, pkt *stack.PacketBuffer) *tcpi return nil } + // If we hit a Hop Limit Exceeded error, then we know we are operating as a + // router. As per RFC 4443 section 3.3: + // + // If a router receives a packet with a Hop Limit of zero, or if a + // router decrements a packet's Hop Limit to zero, it MUST discard the + // packet and originate an ICMPv6 Time Exceeded message with Code 0 to + // the source of the packet. This indicates either a routing loop or + // too small an initial Hop Limit value. + // + // If we are operating as a router, do not use the packet's destination + // address as the response's source address as we should not own the + // destination address of a packet we are forwarding. + localAddr := origIPHdrDst + if _, ok := reason.(*icmpReasonHopLimitExceeded); ok { + localAddr = "" + } // Even if we were able to receive a packet from some remote, we may not have // a route to it - the remote may be blocked via routing rules. We must always // consult our routing table and find a route to the remote before sending any // packet. - route, err := p.stack.FindRoute(pkt.NICID, origIPHdrDst, origIPHdrSrc, ProtocolNumber, false /* multicastLoop */) + route, err := p.stack.FindRoute(pkt.NICID, localAddr, origIPHdrSrc, ProtocolNumber, false /* multicastLoop */) if err != nil { return err } @@ -811,8 +833,6 @@ func (p *protocol) returnError(reason icmpReason, pkt *stack.PacketBuffer) *tcpi return nil } - network, transport := pkt.NetworkHeader().View(), pkt.TransportHeader().View() - if pkt.TransportProtocolNumber == header.ICMPv6ProtocolNumber { // TODO(gvisor.dev/issues/3810): Sort this out when ICMP headers are stored. // Unfortunately at this time ICMP Packets do not have a transport @@ -830,6 +850,8 @@ func (p *protocol) returnError(reason icmpReason, pkt *stack.PacketBuffer) *tcpi } } + network, transport := pkt.NetworkHeader().View(), pkt.TransportHeader().View() + // As per RFC 4443 section 2.4 // // (c) Every ICMPv6 error message (type < 128) MUST include @@ -873,6 +895,10 @@ func (p *protocol) returnError(reason icmpReason, pkt *stack.PacketBuffer) *tcpi icmpHdr.SetType(header.ICMPv6DstUnreachable) icmpHdr.SetCode(header.ICMPv6PortUnreachable) counter = sent.DstUnreachable + case *icmpReasonHopLimitExceeded: + icmpHdr.SetType(header.ICMPv6TimeExceeded) + icmpHdr.SetCode(header.ICMPv6HopLimitExceeded) + counter = sent.TimeExceeded case *icmpReasonReassemblyTimeout: icmpHdr.SetType(header.ICMPv6TimeExceeded) icmpHdr.SetCode(header.ICMPv6ReassemblyTimeout) diff --git a/pkg/tcpip/network/ipv6/ipv6.go b/pkg/tcpip/network/ipv6/ipv6.go index 38a0633bd..7697ff987 100644 --- a/pkg/tcpip/network/ipv6/ipv6.go +++ b/pkg/tcpip/network/ipv6/ipv6.go @@ -645,6 +645,18 @@ func (e *endpoint) WriteHeaderIncludedPacket(r *stack.Route, pkt *stack.PacketBu // forwardPacket attempts to forward a packet to its final destination. func (e *endpoint) forwardPacket(pkt *stack.PacketBuffer) *tcpip.Error { h := header.IPv6(pkt.NetworkHeader().View()) + hopLimit := h.HopLimit() + if hopLimit <= 1 { + // As per RFC 4443 section 3.3, + // + // If a router receives a packet with a Hop Limit of zero, or if a + // router decrements a packet's Hop Limit to zero, it MUST discard the + // packet and originate an ICMPv6 Time Exceeded message with Code 0 to + // the source of the packet. This indicates either a routing loop or + // too small an initial Hop Limit value. + return e.protocol.returnError(&icmpReasonHopLimitExceeded{}, pkt) + } + dstAddr := h.DestinationAddress() // Check if the destination is owned by the stack. @@ -663,13 +675,20 @@ func (e *endpoint) forwardPacket(pkt *stack.PacketBuffer) *tcpip.Error { } defer r.Release() - // TODO(b/143425874) Decrease the TTL field in forwarded packets. + // We need to do a deep copy of the IP packet because + // WriteHeaderIncludedPacket takes ownership of the packet buffer, but we do + // not own it. + newHdr := header.IPv6(stack.PayloadSince(pkt.NetworkHeader())) + + // As per RFC 8200 section 3, + // + // Hop Limit 8-bit unsigned integer. Decremented by 1 by + // each node that forwards the packet. + newHdr.SetHopLimit(hopLimit - 1) + return r.WriteHeaderIncludedPacket(stack.NewPacketBuffer(stack.PacketBufferOptions{ ReserveHeaderBytes: int(r.MaxHeaderLength()), - // We need to do a deep copy of the IP packet because - // WriteHeaderIncludedPacket takes ownership of the packet buffer, but we do - // not own it. - Data: stack.PayloadSince(pkt.NetworkHeader()).ToVectorisedView(), + Data: buffer.View(newHdr).ToVectorisedView(), })) } |